The configurations are identical, and as per the tutorial the ISPConfig databases are mirrored, and mail and web data is synchronised between /var/www and /var/vmail using Unison.

My concern is that while ISPConfig allows the creation of mailing lists via Mailman that these aren't synchronised between servers.

A few questions spring to mind:

1) If a mailing list is set up on one server via ISPConfig, this config change will be mirrored to the other server. Will the other server set up the list when the ISPConfig cron job runs?

2) There is presumably no issue in adding /var/lib/mailman to the list of Unison sync folders so that the archives and list data is copied to the mirror server. Or is there?

3) If two Mailman instances are running for the same list, synchronised regularly, is there a danger in having Mailman running on both machines? Could it cause some sort of cosmic singularity?

This also seems like something that should maybe be in the how-to itself, as the mailing lists are part of ISPConfig's functionality and pretty much everything else seems to be adequately covered in the how-to as it stands.